Telephone-exchange system



Dec. 7,1926. 1,609,339

S. B. .WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed D80. 29 19?4 8 s t s t 1 Dec. 7, 1926. 1,609,339

. S. B. WI LLIAMS TELEPHONE EXCHANGE SYSTEM F'iled Dec. 29. 1924 8 SheetS-Shet 3 smw/ a W/ /Mm I by A/l) Y Dec. 7, I926. I 1,609.339

s. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Dec. 29. 1924 8 sheets sheet 4 Dec. 7 1926. 1,609,339

, s. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed D96. 29 1924 8 s t sh t 5 by MAW Dem 7,1926. I soasss S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Dec. 29. 1924 8 Sheets s5eet 6 Dec. 7 1926. 1,609,339

s. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Filed Dec. 29 1924 8 s 7 1 1-" -7-1 -l I I I i i 1 l {Q i l I --l I I I r: l l

I II I L J H I IrJL (Sd 4/6/19. W/Wm/m; by Af/y' S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM Fi1edD'ec.29. 1924 8 Sheets sheet 9 Patented Dec 7, i926,

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n. A conronarron or new on rnnnrnorin nxcnancn sYsrnM Application filed December 29,1924. serial no; 758,540.

This invention relates to telephone exchange systems, and more particularly to that class of telephone systems wherein antomatic switching apparatus. and automatic switching controlling apparatus are -em-= ployed in the estcblishment of conversational connections.

It has been the practice heretofore in telephone systems WllGIQlIlcalling and called subscribers lines are located in different offices, and wherein no direct trunks 1nterconnect these oflices, to employ so-called tandem switches located at an intermediate oridem office.

a Systems of this character have been devised whereln an'intermediate cc and as a tandem office. Insuch systems, apparatus at the intermediate office distinguishes theclasses of calls undergoing completion. If the called line is located'in he intermediate oflice; local switchessar e operated, whereas if the called line is located in a succeeding office, other classes of switches are operated. In such systems, it has been necessary to transfer the complete designation or a substantialportion thereof from the originating office to the intermediate office regardless of whether this intermediate ofiice is to function as a terminat ing or as a tandem office.

it is an object of the'invention, therefore, to enable an office which is adapted to function as a terminating oflic'e and as a tandem office to discriminate between the different classes of calls requiring extension prior to the reception of the line designation from the originating office. a. feature of the invention relates to a registering and impulse generating mecha- .111 which automatically transmits a discriminating digit to a-distant office prior to the transmission of the line designation.

Another feature of the invention relates to a common registering and controlling I; iechanism which is-adapted to control the completion of local and tandeni'connections, he discrimination between the different classes of connections being accomplished prior to the registering are lin'e 'designw tion in said mechanism. I

A still further feature refers to a telephone ci'iice wherein difier'ent types of eg-is tering and controlling sender's are-employed,

certain conditions causes o e may function both as a terminating lector switch.

or this figure shows a coordinatesenderse whereby s'eizureof one type-of sender under the seizure of another type of sender in? the same. Ones; 7

Other features and advantages of the invention not specifically mentioned will become apparent after a consideration of the fp'llowing description and the. appended claims. 7

Y Referringto the drawing,

Fig. 1, in the upper left corner, shows'one of a number of subscribers lines terminatin in; a coordinate line'swi'tch from which trunks lead to district switches, one of which is "shown in the upper figure. I In the lower figure s showna coordinate sender right portion of this selector switcli,-'while in the lower right-hand por-;

left portion of this tion are shown a district trunk connector and a distric'tframe connector;

Fig. 2, in the upp'erportion, shows-in comparative detail an intcroliice incoming as an interoliice incoming se- The lower leftshand portion lector switch similar-to switch 150 whereas the lower right-hand portion shows a trunk connector and a frame connector. The apparatus disclosed in 2 is located in an' office which is distinct from that including the apparatus shown in Fig. 1.

Fig. 8, in the central portion, shows .a tandem district selector switch located in the same oliice with'switch 200. This figure also represents schematically a tandem sender selector, a tandem sender, an outgoing marker and various connecting devices.

Fig. 4 shows the impulse generating and controlling equipment of the sender located at the originating ofiice. This figure also ilhistrates'certain class relays.

.Fig. 5 to-the left and below the broken line shows a: sender connector and-a portion of an'incoming marker. The remainder of this figure, illustrates a portion of an outgoing Inarlrer, and aschematicrepresentation of; a sender connector.

rig. *6 shows the-various registers located inth'e originating sender.

Fig. 7 shows an incoming sender.

Fig. 8-" show"s algener'ali arrangement of the switching apparatus embodied in apr'e-' fcr'ed form fo'r 'arryinjg out the invention.

Fig. 9 isfaagrain showing"tire-manner should be organized.

General description.

The invention is shown as applied to telephone systems of the general character disclosed in the patentto S. B. Williams, No. 1,517,331, granted December 2, 1924, and also in the copending applications of S. B. lVilliams and E. S. Gibson, Serial No. 645,- 011, filed June 13, 1923; S. B. Williams and E. S. Gibson, Serial No. 722,215, filed June 25, 1924 and TV. 703,362, filed April-1, 1924. Reference may be had to these applications for certain def tails of construction and operatioiiof the various switches and connectors, as well as of the senders and markers referred to hereinafter. 'The line switch 100, district switch 160, incoming switch 200, tandem district switch 300, as well as the sender selector switches 150, 250 and 310 are of the coordinate type, such as shown and described in detail in the British patent to iVesternElec tric Company, Ltd. No.183,438, accepted September 6, 1923 and also in the abovementioned patent to Villiams. The various connectors 170, 180, 230, 240, 500, 571, 340,

360 and 370 consist of groups of multi-contact relays which are adapted, to be'actuated by means of non-interfering start circuits. I v

. Referring to Fig. 80f the drawing, a description will now be given of the general arrangement and functioning of the switching apparatus embodied in a preferred form for carrying out the invention. It will be noted upon inspection that the drawing of Fig. 8 is divided into sections by means of broken lines. The apparatus to the left of the lef hand broken line is situated in an otfice which will be described herein as the originating ofiice. The apparatus shown between the broken lines is situated at a second ofiice which is adapted toezrtend connections to local subscribers lines and to extend connections from the first OlllCG to oifices beyond. The rectangle to the right of the right-hand broken line represents one or more succeeding' ofiices wherein subscribers lines terminate.

For the purpose of securing relative siin plicity in the drawing, the subscribers lines, as calling lines, are shown as appearing in the first office but it will be readily understood that other subscribers lines terminate in the intermediate and succeeding oilices. It will be assumed, therefore, that the sub scriber of line 801 has initiated a call, re sulting in the automatic operation of line switch 800, whereby an idle trunk, as trunk 802, leading to the district switch 803, is seized. Coincident with the seizure of such a trunk, sender selector switch 804 is actuated, whereupon an idle sender, as 805, is

W. Carpenter, Serial No' eos, as

associated with the calling line. For the present, it will be assumed that the wanted line islocated in the office represented between the broken lines. Tie calling 'subscriber having dialed the office code and nu; merical designation of the wantedsline, the registers of the sender 805 are correspond-- ingly set. As soonas the thousandsdigit is thus recorded in thesender, a connecting device, or sender connector 806 is actuated, associating an idle marker 807 with the sender 805. The record of the Oll'lCeCOde is then transferred to corresponding registers in the marker 807 wherein it is translated to mark for selection a particular group of trunks leading from the district switch 803 to the called ofiice. The translation in themai'ker results in the setting of a preliminary or class of service registers in the sender 805; [it the time the marker is associated, the frame connector 808 and trunk connector 809 are selectively actuated. Connector 808 associates the links of switch 803, before which trunk 802 appears, with testing equipment in the marker. Likewise, connector 809 associates the "test conductors of theinarked group of equipment, A

trunks with the same testing link giving aca result of this test, an idle cess to an idle trunk, as811, is selected and the corresponding horizontal magnet is operated, thus establishing connection with the interofiice trunk.

'TVhen thev trunk has been seized, the connectors 808, 809, marker 807. and connector 806 are released. The sender 805 remains engaged and having previously received certain class information as a result of the markers'translation of the office cone, the sender now prepares itself for the transmis sion of series of code impulses. These class indications in the sender not only indicate the necessity of sending code impulses but may also indicate that the called line is located in the same oifice to which the impulses are to be sent. It is to be noted that some indication must be given to the recording sender at the otlice wherein trunk 811 terminates informing such sender that the called line is located in thesame office there with, since certain of the switches in this office are adapted to extend trunk 811 through this office to succeeding orl'ices. As soon as trunk 811 is seized, the incoming sender selector switch 812 is actuated and an idle incoming sender 818 is attached. Send er 813 comprises a number of registers. one of which acts as a discriminating register, the remaining registers recording the lily merical portion of the called line designs tion.

The class information, r'eceivedlg, the sender, determines the character the impulses whichare sent prior to the transmission of the line designation. Since the called line located in the same c iice with lit:

1, coo-see sender 8'18, a preliminary digit, for example the. digit-'- 0, is automatically trans.

sender 805 prior to'the transmission of the line designation. This 0 digit is then recorded on the discrimin ating. register insendor 818 and the numerical record is compl-etely transferred from sender 805 to sender 818. The sender connector 814 is there upon actuated to associate an idle incoming marker 816 with sender 81 8 and the numerical record is transferred from the send or to the marker registers. The thousands digit determines the selection of a group of trunks including trunk 81? leading to a particular final switch 815, whereupon the line marker 818 is associated with the sender and the record of the hundreds, tens and units digits is transferred thereto from the sender 818-. At this time, the connectors 822 and'828 also areopeii ated'. The record in the line marhe results in the selective operation of the incoming and final switches 810 and 815, whereby connection is complet-ed with the called line. During the connection, connectors 808, 809, 819, 821, 822, 828, 882 and 888, and sender selectors 804 and 812 and senders 805 and 818 are released together with the incoming marker 818 and the line marker 818.

Should the called subscribers line be located in an ofiice beyond and to which no direction trunks lead from theoiiice in which line 801 is located, then the connection is extended over a trunk similar to trunk 811, terminating in an incoming switch as 810. In this case, however, the oiiice containing switch 810; must in order to complete the connection to the office beyond. Accordingly, prior to the transmission of im ulses in accordance with.

the setting of the office code and numerical registers of sender 805, apreliminary digit in this case 1 is transmitted by means of code impulses to the preliminary register in sender 818. The digit 1 is recorded in sender 818 and serves to indicate to said sender that the call is of the tandem class. As soon.

as this preliminary digit is received, the inn-.- pulse generating mechanism at the origin-ating oflice is stopped, thus preventing the.

sending of further impulses to sender 818. The recording of the digit 1 at sender 818 also causes incoming switch 810 to: be actuated, whereby a trunk 824 leading to a tandemv district switch 820 is selected. Tm,-

mediately that this trunk isseized, the con-v nectors-81t, 819, 821and the incoming mark er 816 are released and revert to common use. Sender 818 however, remains engaged.

The seizure-of trunk 82 1 also causes sender. selector switch 826 to operateito associate-- an. idle tandem sender. 27' with-theincoining' The. tandem. sender. haringi been, thus -attached,. an indication is; given; .to; the";

trunk.

function as a tandem oiifice originating sender 8Q5 Wl11l1 thereupon proceedsto transmit the: complete designation of the wanted line through the sender 818 to the registers of the tandem sender Meanwhile, the impulse receiving relays in the incoming sender 818 have been cut out of circuit and a pulse counting combination substituted thereior, so that when the complete number 0515 impulses have been transmitted to the tandem sender, sender 818 and switch 812 may release. Upon the receipt of the oiiice code and thousands digit by sender 82?,connector 828 is actuated to assodate an idle. marker 829 therewith. The oihce code record is thereupon transferred from sender 827 to marker 829, wherein it is translated. At this time connectors 882 and 888 are also operated. The translation of the otlice code causes the tandem district selector switch 820 to seize oneot a number of trunks as 881 leading to the called oilizc. The seizure of this trunk causes connectors 882', 888', 828 and marker 829 to rel-ease, the tandem sender 827 remaining engaged. in the manner described in the copending 113- piication of S. B. Williams and 8. Gibson Serial No; ($425,011, filed June 18, 1928, the record of the wanted line is next transferred from the sender 827to an incoming sender in the called oii ice, resulting in the selective operation of incoming and final switches, and seizure of the called line.

Detailed description.

It will be first assumed that the subscriber at station 101 has initiated a, call for the purpose of communicating with a. subscriber whose line is located in a distant cities to he reached without the use of tandem switchm ing apparatus. When the calling subscriber removeshis receiver trom its switchhooh, line switch is actuated to extend the call ing line to an idle district trunk 151, whereupon the conductor 152 is grounded causing the energization ofrelay 102. The operation of relay 102 in turn causes the sender selector switch to be actuated whereby an idle sender such. as shown in Figs. 1 and 6- is associated withthe calling line. As soon as a sender has'been thus associated, and 1 with the start relay 102 operated, a record is made in the senderof the group of district switcheswherein trumr 151 terminates. The circuit for this purpose may be traced from battery through, the winding and normal contacts of relay did, right contacts of relay 4107, conductor-. 158, contacts of switch 150, inner. armature and front contact of relay 102 to ground through the cross connection block. 117. B elay 41d; relates to the connecting device? ?,whi-ch is.capable-ofassociating, any district switch in the-group including switch; 160, with the marker; shown in Fig. 5:. Relay-4:141; llnlilediately looks through its wuidingzand oelringigcontach Q pect r- 453, which was grounded when the sender was seized. A short interval after the association of the sender, the start relay 102 is released, but the connection of the sender with the trunk 151 is maintained by the continued energization of a horizontal magnet as 157. The tip and ring conductors of the calling line are now extended through contacts of switch 150 to the impulse receiving mechanism 400. The calling subscriber thereupon is notified by a characteristic signal that the circuits and apparatus are in readiness for the reception of series of dial impulses. F or the purpose of description it will be assumed that the code of the oiiice in which the called line is located is GER. In dial impulses this code would be represented by series of 4, 3 and 7 in'ipulses, respectively. The first series of 4 impulses having been transmitted by the calling subscriber is recorded upon the counting relays of the receiving device 400. For a detailed description of the manner in which the foregoing operations are effected, reference may be had to the patent to S. B. l l illia-ms, No. 1,517,331, issued December 2, 1924.

.Vhen the sender is attached to the calling line as mentioned above, ground is extended through the'contacts of relays 415 and 601, to battery through the winding of relay 602. Relay 602 is immediately locked by means or" a circuit which is completed through the windlng and locking contact thereof, conductor 657, winding of relay 415,

" to control ground. Relay 415 does not operate in this circuit however, because of the existence of the shunt produced by the previously traced operating circuit of relay 602. l Vith relay 602 operated the windings of the relays of register 610 are connected to the impulse receiving mechanism 400, and since the first letter of the 015cc code has been assumed to be G, conductor 653 is grounded, thus causing the operation of register relay 603. Relay 603 immediately locks to the grounded conductor 652, and extends this same grounded conductor through the left outer contacts of relay 603 to batterythrough the winding of relay 601 which operates and also locks to conductor 652. Relay 601 in operating opens the operating circuit of relay 602 remqving the shunt from around the winding of relay 415. Relay 415 thus operates in series with relay 602.

in the manner described in detail in the above mentioned patent to S. B. Williams, No. 1,517,331, the operation of relay 415 at this time causes the release of the operated counting relays corresponding to the first series oi impulses transmitted, whereupon relays 415 and 602 in turn are released. With relay 415 normal a circuit is completed from battery through the winding of relay 604, back contacts of relay 609, front contacts of relay 601, conductor 451. contacts of relav 415 to ground. Relay 604 is similar in function to relay 602 and serves to connect the counting relays 400 to the relays of register 620. Relay 604 also locks in series with re lay 415 which fails to operate because of the shunt circuit which has already been traced. The second series of impulses corresponding to the letter E, as recorded on the counting relays, results in the grounding of conductors 654 and 655 whereby register relays 605 and 606 are operated. Relays 605 and 606 immediately lock to the grounded conductor 652. A circuit is thereupon closed for relay 609 which also looks to conductor 652 and removes the shunt from around the winding of relay 415 in a manner similar to that described in connection with relay 601. Thus relays 604 and 415 are locked in series to the grounded conductor 652. Relay 415 in operating, as mentioned hereinbefore, causes the release of the operated counting relays, whereupon both relays 604 and 415 release.

Relay 612 is now operated over a circuit which is completed through the back contacts of relay 611, front contacts of relays 609 and 601 to conductor 451. The third series of impulses corresponding to the letter 1% are now received by the counting relays, causing conductors 651 and 655 to be grounded and resulting in the operation of relays 607 and 608 which look. Relay 611 is now operated and brings about the actuation of relay 415 in series with relay 612, whereupon the counting relays, and relays 415 and 612 are successively deenergized. In a manner similar to that above described succeeding series of impulses as received by the counting relays are transmitted to succeeding numerical registers the first of which, namely the thousands register, is shown in comparative detail, while the remaining numerical registers are represented by the dotted rectangle 670. When relay 611 operates it closes a circuit traceable from battery through the winding of relay 407, conductor 463, contacts of relay 611 to the grounded conductor 652. Relay 407 operates in this circuit and serves as an indication to the sender that the oiiice code por tion of the called line designation has been registered, and the sender is now in readiness .to be associated with an idle switch controlling marker.

It will be assumed that the marker shown to the left of, and below the broken line of Fig. 5 is idle, when relay 407 operates. A circuit is therefore completed from battery through the left winding of relay 501, conduct-or 454, baclr contacts of relay 408, left contacts of relay 407 to ground. Relay 501 is a start relay and functions to bring about the selective operation of connector 500 by first causing the operation of multicontact'relay 502. Eelay 503 is also actuated in. the manner described in detail in the ap I 703,362 hereinbefore referre W. W. Carpenter, Serial No.

d to. With relays 502 and 503 operated, registers 610, 620

and 630 are associated with corresponding registers 510, 520, 530 in the marker.

plication of Transfer of record from the sender to the marker and the selection of an outgomg trunk.

As soon as operated, the conductor 454 is extended by means of contacts of this connector to battery through the winding 01 marker ground control relay 504. Since relay 603 of the first register is operated a circuit is completed for operating relay 505. This circuit may be traced from battery through the winding of relay 505, contacts of connector 500, conductor 757, right outer contacts of relay 603, conductor 459, returningthrough contacts of connector 500, thence through the left contacts of relay 506 to ground at the armature of relay 504. Since relays 605 and 606 ofv the second register are operated similar circuits are closed for corresponding relays 50? and 506 in-the marker. Likewise circuits may be traced for relays 509 and 511 corresponding to the operated relays 60? and 608 of the third sender register. The record of the otiice code having thus been transferred to the marker, the translating device 550 is selectively actuated'in accordance with thisrecord to cause conductors 551, 552 and 550 to be grounded. 7 The grounding oi conductor 551 causes the operation of relay 512. Belay 512 closes obvious operating circuits :torv relays 416, and 429 in the sender. The grounding or" conductor 552 causes relay 417 to operate. These relays upon operating close locking circuits which are completed to the grounded conductor 453. The operation of relays 416, 417 and 429 serves to indicate to the sender the class oi call requiring extension, so that the raid sender may subsequently adjust itself "for controllingthe sending of code impulses to the recording sender at a succeeding oriice. The actuation of translator 550 also causes conductor 553 to be grounded whereby relay 513' is operated. Belay is individual tov the group of trunks leading from district switch 160, including trunk 161, which leads in the direction of the called oiiice. Relay 524 is another group relay and may be operated when a different o'iiice e de is recorded on the registers 510, 520, etc. Since there may be a plurality of district switches itbecoines necessary to distinguish to the mark r the particular switon wherein the trunh151 terminates. Accordingly trains connector start relay 103 is operated in a circuit traceable "from battery at the col conductor 5157, winding/of relay 103, con

ctor 5V6 contacts of connector-500 rioiit the connecting device 500 has be traced from t 1e windings inagnet throughthe winding of relay 112.

eration of relays 111 and 112 ZtSSOCll'tQStlEO act of relay 506,

front contact otrelay 4:14, conductor 459,

contacts oi connector 500,- to ground awn armature of relay 504. Relay 103 n turn brings about the actuation of a common relay 104., whereby ground is extended through the contacts of this latter relay to operate rnulti-contact relay 10.5.

It is to be observed that tl e not 106, which controls the vertical row of contacts in switch 160 association of. the marker with the sender. The c rcuit for operating magnet 106 may thereof, through contacts of relays in the trunk circuit 151 v(not shown), outer armature and back contact of relay 102, of switch 150, conductor 457,1conductor 458, contacts of connector 500, conductor 559, contacts of relay 105, conductor 459, to ground at an armature of relay 504. This same ground for operating magnet 106 is extended through the lower contacts thereof and thence j to battery through the winding of inulti-contact relay 107-. The operation of relays 105 and 107 associates, with the marker testing equipment 570, a conductor from each of the hori zontal links and a conductor from eachof tal magnets 'in'switch 160. When relay 103 operated as mentioned hereinhetore' ground was extendedover conductor 461, lay 513, conductor 462 to the winding of relay 108. Relay108 is associated with the trunk connecting device- 180 and acts asa start relay for causing the selective operation of this connector; atlay 108 also causes the actuation of relay 109 as described in .the above mentioned application of W. W. Carpenter, Serial No.

703,362, whereby n'iulti-contactrelay 111 is subsequently operated. erated, a circuit is'clo'scd for operating the trunk vertical: magnet 114 which controls the Vertical row ot co'ntacts selected group of interoriice trunksterminates. The circuit for this purpose may be traced from battery through the winding of 114, contacts of relays 10'. and 105,

conductor 162, left inner contacts of relay 513, conductor 562, contacts of relay 111, This sameground 18 extended through the contacts or returning thence to ground.

relay 108 over conductor 563, right contacts of relay 513, conductor 564. to battery The optest conductors oft-he trunks in the selected group with the marker test relays 570.1 In the manner described in detail in the above mentioned application oil l W. Carpenter, the marker test relays 5Y0 determine .an'idle cross point-throughswitch 100. This cross vertical anagwherein trunk 151 terminates, was operated subsequent toythc battery through the winding returning thence to of the corresponding horizon through-the contacts thereof lett outer contacts of rebattery through lVith relay 111 op in :which the.

contacts 1 winding of relay 419, and thence I as above traced by means of the outer conpointincludes a link, for example link 118, before which appears an idle interoflice trunk as 161. The horizontal magnet 116 corresponding to this idle. cross point is thereupon energized and the trunk 161 is seized.

The marker having completed its function in the controlling of the selection of an interofiice trunk is now released and may revert to common use. The release of the marker may be initiated by the operation of relay 408. The manner in which the marker controls the selection of an outgoing trunk and the manner in which the said marker is released upon the. seizure of said trunk is fully described in the above mentioned application of 'W. W. Carpenter, Serial No.

708,862 to which reference may be had fora detailed description of operation of the connectors 170 and 180, as well as of the switch 160, these having been described herein in a comparatively general manner.

hen relay 408 operates, subsequent to the seizure of trunk 161, a circuit is completed from battery through the winding of relay 401, left contacts of relay 416, right contacts of relay 408, left contacts of relay 407 to ground. Relay 401 immediately locks to the grounded conductor 458. The actuation of relay 401 prepares the sender for the transmission of code impulses to the distant office. Relay 401 also completes a circuit from battery through the right winding of relay 202, right contacts of relays 201 and 204, thence over the tip side of trunk 161, through contacts of switch 160, tip side of trunk 151, contacts of switch 150, conductor 457, left inner contacts of relay 401, right'contacts of relay 419, winding of relay 409, left contacts of relay 419, left outer contacts'of relay 401, conductor 456, contacts of switch 150, over the ring side of trunk 151,'through contacts of switch 160, over the ring side of trunk 161, left contacts of relays 204 and 201, to ground through the left winding of relay 202. Relays 202 and 409 operate in this circuit. Relay 202 closes an obvious operating circuit for relay 208. Relay 208 is a relay similar to relay 102 andwhen actuated causes the sender selector switch 250 to as ociate an idle incoming sender, such as shown in Fig. 7, with the incoming trunk 161. With relay 409 operated, a circuit is completed from battery through the winding of relay 418, contacts of relay 409, back contacts of relay 420 to ground over conductor 458. Relay 418 also closes aholding circuit which is completed through the to ground tacts of relay 418. Relay 419 is shunted by the operating circuit described for relay 418 and does not operate at this time. When the sender at the distantoflice has beenassociated with thetrunk, ground is returned over the conductor 7 52, thence through contacts of switch 250 to operate relay 204. Relay 204 causes the release of both relays 202 and 409. The release of relay 409 removes the shunt from around the winding of relay 419 and this relay operates in series with relay 418. If the thousands digit has been recorded, then relay 614 op rated, whereupon a circuit is completed from battery through the right winding of relay 428, left outer back contacts of relay 424, left inner contacts of relay 626, front contacts of relay 614, conductor 661, front contacts of relay 418, back contacts of relay 420, to the grounded conductor 458. Relay 4* Z connects ground through i ts inner right con tacts, left outer back contacts of relay 4%, right outer contacts of relay 411, right outer contacts of relay 421, left out-er contacts relays 418 and 404, inding of relay 408, to battery at the contacts of relay 402. lielay- 408operates and closes an obvious cnergizing circuit for relay 404. Relay 404 closes a locking circuit for itself which may be traced from battery through the left winding and left locking contact of said relay, to ground through the left outer armature and back contact of relay 411. he lay 404 by means. of'its right middle con tacts provides a locking circuit for relay 428 which is completed through the left winding and locking contact of relay-428. When relay 404 operated, it also closed a circuit for operating the connecting relay 628 of the preliminary register relay 625. The circuit for this purpose may be traced from battery through the winding of relay 628, right baclrcontacts of relay 62?, right inner contacts of relay 429, contacts of relay 426, to ground at the middle contacts of lay 404. Relay 628 looks in series with the winding of relay 426 to the same ground. However, the operating circuit described for relay 628 acts as a shunt around the windmg of relay 426 and this relay fails to operate. The operation of relay 404 also causes the release of relay 408 whereupon the inipulse timing relays 412 and 418 are started in operation. The circuit for operating relay 412 inay be traced from battery through the winding of relay 412 left inner back contacts of relay 418, right outer contacts of relay 404, left inner contacts of relay 408, to ground at .an armature of relay 41,9. -When relay 412 has attracted its armatures, it completes a circuit from battery through thewinding of relay 418, thence through the left inner front contacts of relay 412 150 ground as above traced. Relay 418, extends this same ground through its right contacts, thus shunting the winding of relay 412 which begins to release. l fhenrelay 412 has retracted its armatures completely, the

above traced circuit for relay 418 opened and this relay begins to release. The characteristics of relays 412 and 413 are such that their arniatures are attracted and retracted in a relatively slow manner. This cycle of operation and release or relays 412 and 413 is continued until all the required impulses have been transmitted. VVh'en relay 412 first operates, a circuit is closed from battery through the left Winding otrelay 411, winding of relay. 421, inner l'e'it baclr contacts of relay 411, to ground at the left outer contacts of relay 412. Relay 421 operates in this circuit, but relay 411 being marginal fails to operate. When relay 421 operates, it completes a circuit through they lett Winding of relay 411, Winding of relay 421,1ight Windi of relay 411, rightinn-er contacts of re 421 to the grounded conductor 453, relay 411 re nains shunted and fails to operate. during the first cycle, the shunt is removed from the windings of relay 411 and this relay operates in series with relay 421.

Prior to the completion of the first of operation and and subsequent to the deenergization of relay 412, circuit is completed from battery at the contacts of relay 402, Winning of relay 406, left inner contacts of relay 421,

left inner back contacts of relay 412, right outer contacts of relay 404 to ground through contacts of relays408 and 419. Relay 406 loclrs through its Winding and locking contacts, hence through the left outer armature and front contact of relay 411, to ground at the righ inner contacts of relay 423. The operation of relay 406 opens the impulse circuit and re"erses the connection of the tip and ring conductors of the trunk with the impulse mechanism. It will be noted that when relay 41-1 operated, a circuit was completed from battery through the ight Winding of relay 422, winding of right baclr contactso't relay 422 ound at the right inner contacts of re- Relay operates in this circuit receives insulhcient current and During the first impulse 'od no code iinpulse is transmitted to Relays 412 and 413 undergo another cycle o eration and release for the purpose of the second iinpulse period. l Vhen 12 operates at the beginning of the cycle, direct locking circuit is comthrough the left Windin of relay thus shunting relay 421 Which releases. During this period, the operation ot relay closes a circuit from battery through he high resistance 671, condu I outer front contacts of relay 406, lett outer back contacts of relay 403, left outer contacts or" relay 401, thence by means of contacts of switches 150 and 160, tothe ring conductor of trunk 161, through-contacts of cause or the inclusion therein or When relay 412 releases release of relays 412 and 413,

switch 250, conductor 753, right outer contacts of relay T02, baclr contacts of relay 7'03, windings otrelays 1'05, 708 and 709 in series, right inner contacts of relay 702, right back contacts of relay T01, conductor 759, returning by means of switch 250 to the tip conductor of trunk switches 160 and 150, inner lett contacts of relay 401, rin'ht back contacts of relay 403, inner right front contacts of relay 406, left outer cont-acts of relay 423 to ground at the arinatur'e of relay 419. lhe direction of flow of the current in this circuit is such as to cause the operation of relay 708, but bethe high resistance 6T1, marginal relay YOoreInains normal. Relay '(08 extends the grounded conductor 751 through the contacts 01' the said relay, rightbaclt contacts 0t relay right ninding 0t relay 71.0, to battery through the right winding of relay 707. Re lay 710 operates in this circuit but relay 707 receives insufficient current to cause the energization thereof. l lelay T10 completes circuit from battery through'the Winding 0'1 relay 712 left on be cl; contacts 714, left ifront contacts of relay 710 to the grounded conductor T51, lt'elay 712 operates and closes a circuit through its windine' and the winding oi relay i 14, thence throng l theleit outer front contacts of relay 712 to ground as above traced. Relay 714 is shunted however, and does not operate in thiscircuit. Prior to the end of the second impulse period, releases thus opening the holding circuiof relay 411 which also releases. Relay 411 in turn brings about the release of relay 406, thus opening the impulse circuit a i'i'd causing relay '205 at the distant ofiice'to retract its armatures. The release oi relay 411 re rieves the shunt from around the winding of relay "422'and this relay now operates inset es with relay 427. At the termination of the second imalso period, relay 413 retracts its armature. Relay 404 having released when relay 412 retracted its an iring the second .zinatures period, a circuit isnow closed for relay 403 by rneans or a path which has been hereinbetore traced. Relay 403 rounds both sides of the impulse circuit for the purpose of discharging electrically, the metallic conductors thereof, and also closes an'obvious circuit for relay 404 which locks over a circuit hereinbetore'traced. Relay 404 in turn causes the release of relay 403 and the inipulse circuit is again prepared. When lay 708 released,= des ibed above, the shunt. was removed from around the winding of relay 707 and this relay operates in series'withfrelay 710. Belay 710 remains operated in this circuit so that the shunt is maintained around' the Winding or relay 714. -When relay 422 operates as above described, a circuit is closed from battery of relay 161, through contacts of i through left winding of relay 428, Winding of relay 405, left back contacts of relay 428, left front contacts of relay 422, left contacts of relay 402, to ground at the left bacl: contact of relay 421. Relay 405 operates but relay 423 being marginal does not operate. Since relay 406 is normal during this period however, the impulse circuit is open and the recording relays at the distant oflice are not ali'ected.

The operation of relay 412 during the third impulse period causes relay 421 to reoperate, but relay 411 is shunted and remains normal. Prior to the end of the third period, when relay 412 releases, it opens the shunt around the winding of relay 411, which operates in series with relay 421. Relay 411 completes a direct locking circuit to battery through the left winding of relay 422, thus shunting relay 427 which releases. The operation of relay 421 at this time opens the shunt from around the winding of relay 428 which now operates in series with relay 405. At the end of the third period with relays 412 and 413 normal, a circuit is closed for operating relay 406 for purposes hereinbefore described. Relay 406 looks, and relays 412 and 13 undergo a fourth cycle of operation and release. The operation of relay 412 at the beginning ofthis cycle causes the release of relay 421 by shunting the same. Relay 421 in turn closes a direct locking circuit for relay 428, causing relay 405 to release. Since relay 406 is operated, the previously traced circuit, including the high resistance 671 and relays 705, 708 and 709, is again completed resulting in the reoperation of relay 708. Relay 708 upon operating closes a direct locking circuit for relay 707 and shunts relay 710 which releases. Prior to the termination of the fourth period when relay 412 has released, the holding circuit of relay 411 is opened and this relay also released in turn, causing the release of relay 422. Relay 422 opens the locking circuit of relay 428 which restores to normal. With relays 411 and 412 normal, relay 404 releases, and when relay 413 releases at the end of the fourth period, a circuit is closed for energizing relay 403 described hereinbefore. Relay 403 opens the impulse circuit and causes the line conductors to be discharged. The impulse mechanism is in readiness to transmit impulses corresponding to the digit recorded on the thousands re ister 640. It will be noted however, that at the end of the fourth per od as described, when the impulse circuit is opened by relay 403, relay 708 at the distant ofiice releases, thus opening the locking circuit of relay 707 which also releases. Relay 707 removes the shunt from, around the winding of relay 714'which operates in series with relay 712 to the grounded con ductor 751.

When relay 427 operated, as above described, a circuit was completed from battery through winding of relay 627, right outer contacts of relay 427 to ground over conductor 453. Relay 627 immediately looks to the ground conductor 652. The operation of relay 627 in this circuit removes the previously described shunt circuit from around the winding of relay 426 which operates in series with relay 623. When relay 404 releases at the endof the fourth impulse period, this locking circuit is broken, whereupon 623 and 426 release. Relays 412 and 413 undergo four more cycles of operation and release for the purpose of timing the impulses corresponding to the thousands digit. Relay 404 operates as hereinbefore described and closes a circuit for relay'616 traceable from battery through its winding, back contacts of relay 626, outer front contacts of relay 425, outer front contacts of relay 629, 634 and 632, right inner front contacts of relay 424, right back contacts of relay 625, front contacts of relay 627 conductor 673, front contacts of relay 429, to ground through contacts of relay 426 and 404. .Relay 616 looks in series with the winding of relay 426. Belay 426 however is shunted and remains normal. Relay 616 as impulse circuit.

it will be assumed that the thousands digit of the called line designation is 1. Accord ingly, relay 617 is operated and during the first impulse period, a circuit is completed from battery through the high resistance 671, front contacts of relay 617, left outer contacts of relay 626, right normal contacts of relay 424, right outer front contacts of relay 423, left back contacts of relay 405, ight normal contacts of relay 406, right back contacts of relay 403. inner front contacts of relay 401, thence by means ofcontacts of switch 150 to the tip conductor of trunk 151, through contacts of switch 160 to the tip conductor of trunk 161, contacts of switch 250, conductor 759, thence through the windings of relay 705, 708 and 709 in se-- ries, returning by means of switches 250, 160

and 150 through the outer front contacts of relay 401, left outer back contacts of relay 403, left normal contacts of relay 406, left front contacts of relay 423, to ground at the armature of relay 419. The direction of flow of current in this circuit is of such a nature as to cause relay 709 to operate. but because of the inclusion of resistance 671, marginal relay 705 remains normal. Vjith relay 709 operated, a circuit is completed from be. tery through the winding of register relay 715, left back contacts of relay 719, left inner front contacts relay 712, right back contacts of relay 710, contacts of relay 709 to ground over conductor 751. Relay 715 immediately locks to the grounded conductor sociates the thousands register 640 with the iic ' ductor .7 51. Relay 751. Since relay 618 of the thousands registeris normal, then no impulse is sent to the distant oflice, operate the corresponding relay 716. However, during this second impulse period, since relay L06 is operated, a circuit is closed from battery through the high resistance 671., left outer front contacts of relay e06, left outer back contacts of relay 403, thence over the ring side through the impusle receiving relays at the distant office returning thence over the tip side of the impulse circuit through the left inner contacts of relay401, right outer back contacts of relay 103, right inner front contacts of relay. &06 to ground through the left outer front contacts of relay e23 as hereinbefore traced. The polarity of the current in this circuit causes relay 708 alone to operate. Relay 708 completes a circuit from battery through the winding of relay 719, left back contacts of relays 720 and 713, left outer front contacts of relay in, left outer front contacts of relay 710,

contacts of relay 708, to the grounded con- 719 operates in this circuit but relay 720 being shunted remains normal. During the third and fourth impulse periods, no numerical impulses are sent, since register relays 619 and 621 are normal. During the fourth impulse period, however,- the above traced circuit including the high resistance 671 is closed, causing relay 708 to operate. Belay 708 by closing a direct locking circuit for relay 707 causes relay 710 to release as hereinbefore described, and at the end of the fourth period when the impulse circuit is opened by relay 4103, relay 708 releases. The release 'of relay 708 in C-Ulll causes the release of relay 707 which removes the shunt from around the winding of relay 720. Relay 720 now operates in serieswith relay 719. The operation of relay 720 transfers the control of the impulse receiving mechanism of Fig. 7, to the second or hundreds register 730. In themanner described in detail in the above mentioned patent ,to S. B. Nilliarnsfllol 1,517,331, the rec 0rd on the hundreds, tens and units registers 670 of the sender of Fig. ,6, is transmitted by means of impulses to cause the operation of corresponding relays in registers 730, 740 and 750. When register 750 has been positioned, relay 75.8 operates. tion of relay 758 extends the grounded conductor 751 through the right front contacts of said relay to battery through the left winding of relay 51 i. Relay 514 is a start relay similar to relay 501 and when energized brings about the operation of the connecting device 571 (similar to connecting device 500), whereby an incoming marker which is partly shown in the upper right hand corner of Fig. 5, is associated with the sender of Fig. 7. When the device 571 is completely operated, conductor 7 51 is exduring the second period, to

No. 7 03,362, the marker operation of the. incoming sw tch 200, where-- The operatended therethrough, causing the operation of marker ground control relay 522. In the manner described in detail in the above mentioned application of W. /V. CarpentnSerial controls the selective by a trunk such as trunk 262 is seized; Trunk 262 is one of a number of trunks which lead to a final selector switch as 260, which has access to called lines in the same 011106,Wl1616 in switch200 is located. For a detailed description of the manner in which the connec tion' may be .completed'to the called line 263 by means of switches 200 and 260 reference may be had to the above mentioned applica-v tion of N. W. Carpenter, Serial No. 703,362.

Ewte'nsion of a connection ivwolving an in? termedz'ate ofiice as a tandem point;

It will now be assumed that the'number as dialled by the subscriber at station-101' is that of a line located in the ofiice represented schematically by the rectangle 350. It will be further assumed that there are no trunks directly connecting the calling and called oii'ices. In this, instance, the recording of the office code on the sender registers 610, quent transferral of the record to the marker registers 510, 520 and 530 as hereinbeforedescribed, will causeconductors 5,53,

554 and 555' to. be grounded. The grounding of conductor 555 causes theoperation of relay 516 whereby the class relays 416, 12 1, and 4l25 are operated. As a result of the ground-ing of conductor 554, the pre liminary register relay 625 is operated. Relay 625 on operating extends. ground through its left out-er front contacts to battery through the winding of relay 4 29. Relays 4:29 and conductor 652. y y

Itwill be assumed that the called office is reached by one of the trunks in the group controlled by relay 513 which is operated as a result of the grounding,ofconductor' The operation of class relay 424C serves to indicate to the sender, that the called office is to be reached by switching apparatus at the intermediate office as hereinbefore described so that the said sender may subsequently adjust itself for the controlling of the switching devices at succeeding offices. In this case, the controlling of switch 160, to seize an interolfice trunk is accomplished in a similar manner to that already described in connection with the seizure of trunk 161.

For the purposes of description, it will be assumed that the line designation as recorded on registers 610, 620 and 630, results in the seizure of trunk 161 whereupon the marker shown in Fig. 5 as well as the sender connector 500, frame connector 170 and trunk connector 180 are released.

620 and 630 and the subse- 625 also lock to the grounded pulses from the sender of Fig. 4 to the sender of the distant oflice. In this case, however, register relay 625 is operated, and the impulses sent, prior to the transmission of the first digit of the office code, are of such a'nature as to indicate to the distant sender that the called line is not located in the same oiiice therewith and that the said office must function as a tandem point. Accordingly, prior to the transmission of the oflice code, the operation of relay 6% causes impulses corresponding to the digit 1 to be sent from the originating office to the office wherein trunk 161 terminates. As soon as *the thousands digit has beenrecorded on register 640 and the marker has released, a circuit is completed from battery through the right winding of relay 423, right front contacts of relay 425, left inner contacts of relay 626, right front contacts of relay 614, right front contacts of relay 418, back con tacts of relay 420, to the grounded conductor 453. Relay 423 immediately looks through its left winding to the same grounded conductor. The operation of relay 423 brings about the successive operation of relay 403 and 404 as hereinbefore described, whereupon the timing relays 412, and 413 begin their cycles of operation and release.

During the first impulse period, a circuit is completed from battery through the high resistance 671, right inner front contacts of relay 625, left back contact of relay 627, right outer fron'rt contacts of relays 424 and 423, left back contacts of relay 405,

right normal contacts of relay 406, thence over the tip side of the impulse circuit through the receiving relays 7 05, 7 08 and 709 at the distant oflice, returning thence over the ring side of the impulse circuit to ground as hereinbefore traced. tion of flow of current in this circuit is of such a nature as to cause the operation of relay 709 alone. Relay 709 completes a circuit from battery through the winding of relay 711, left inner back contacts of relay 712, right back contacts of relay 710 to ground through the contacts of relay 709. Belay 711 immediately locks to the ground ed conductor 751. Relays 711 and 713 form a preliminary or class of service register corresponding to the preliminary register The direc-.

in the sender of Fig. 6. Relay 711 extends grounded conductor 751 through its right 412 and 413 undergo threemore cycles of operation and release as hereinbefore described. During the second period the circuit hereinbefore traced is completed from battery through the high resistance 671, thence over the ring side of the impulse circuit, conductor 753, outer back contacts of relay 702, windings of relays 705, 708 and 709, returning thence over the tip side of the impulse circuit to ground as already traced. Relay708 operates and completes a circuit for relay 710. Relay 710 completes the circuit for operating relay 712 which looks in series with relay 714. Re-

-lay 714, however, remains normal. When relay 7 08 releases upon the opening of the impulse circuit after the third period, relay 707 operates in series with relay 710, relay 714, however, still being shunted. At the end of the fourth period, the circuit above traced is again completed through the wind ing of relay 708, which reoperates and shunts relay 710, the latter relay releasing. VYhen the impulse circuit is opened at the end of the fourth period, relay 708 releases, in turn, releasing relay 707. Bela 714 now operates in series with relay 712 to the grounded conductor 751. Relay 714 in turn operates relays 701 and 703 which dis connect the receiving relays 705, 708 and 7 09 and prepare a new impulse circuit which will be described hereinafter. At the termination of the fourth impulse period, relays 404 and 427 release, thus opening the holding circuit of relays 623 and 426 which also release.

Relay 403 now operates to cause the men gization of relay 412 as hereinbefore described. Relay 403, in turn, operates relay 404 which looks. A circuit is now closed from battery through the winding of relay 420, right back contacts of relay 410, right outer front contacts of relay 625, right front contacts of relays 627 and 429, contacts of relay 426, to ground at relay 404. Relay 420 in operating causes release of relays 418 and 419. Relays 412 and 413 undergo three more cycles of operation and release but no impulses are sent to the distant ofiice because relay 419 is normal. Relay 420 completes 'at an armature of relay 522.

Y relay "523, to ground an obvious operating circuit for relay 410 which upon operating, opens the energizing circuit of relay 420 which begins to release. Relay 410 however is locked to grounded conductor 453. Relay 420 however maintains its armatures in their attracted position'for an appreciable interval.

At the end of the fourth impulse period relays 404, 412, 413, above described, whereby the original operating circuit of relay 423 is broken and this relay retracts its armatures thuspreventing further operation of the timing relays 412 and 413. lVhen relay described it extended grounded conductor 751 through its left inner contact, contacts of relay 704, to battery through the left winding of relay 514 which as hereinbefore mentioned causes the sender connector 571 to associate an idle marker with the incoming sender. With the connector 571 operated, ground is extended over conductor 751 to battery through thewin'ding of ground control relay 522. Relay 521 is now operated by means of a circuit which may be traced from battery through the winding of said relay, contacts of connector 571, conductor 755, left outer front vcontacts of relay through contacts of connector 571 to ground Relay 521 in turn closes an obvious energizing circuit for relay 523. Relay 523 is a relay similar in function to relay 513 but is individual to a group of trunks leading out of switch 200 to a tandem district selector switchsucli as 300. In the manner described in detail in the above mentioned application of V]. N. Carpenter. Serial No. 703,362, relay 206 is energized resulting in the operation of multicontact relays 207 and 208 thereby associating the links of switch 200 with the marker test relays 580. Belay 206-completes a circuit traceable frombat-tery through the wind. ing of relay 209, right outer front contacts of through the contacts of relay 206. A short interval later, relay 211 is energized whereupon multi-contact relay 212 is actuated over an obvious circuit. Multicontact relay 213 is also energized at this timeby means of ground extended through the outer contacts of relay 209, thence through the left inner contacts of relay 523 to battery through the winding of relay 213. Relays 212 and 213 associate the test conductors of the group of trunks,'to which relay 523 is individual, with the marker test relays 580. magnet 216 was operated subsequently to the seizure of trunk 261, whereas vertical mag-net 217 is now energized by means of a circuit traceable from battery through the winding of said magnet contacts of frame connector 230, left outer contacts of relay 523, contacts of trunk connector through the contacts ofrelay 209.

the i 422 and 427 release as 711 operated as above 711, returning It will be noted that vertical 240 returning to ground It willbe' assumed thatlink214 anditrunk 264- are simultaneously idle, then the particular one of the test relays 580 corresponding to this idle'crosspoint'remains normal and asdescri-bed in the above mentioned.application of WV. 1 V. Carpenter, :Serial No. 703,362, the corresponding horizontal magnet 218 is energized, A short interval after magnet 218is operated,irelays526 and 527 'are actuated and serve to release the marker, the sender connector 571 and the, connectors 230 and 240. The sender shown in Fig. ,7 is not released however at this time,

As soon as theconnection is completed with trunkz264 the sleeve conductor thereof is grounded resulting in the operation of relay .302. Relay .302 is gsimilarin functionto relays 102 and 203 and when energized causes the sender selector switch 310 tooperate to associate a tandem sender 320with the extended calling line. The sender 320 now awaits the receipt of code impulses from the calling oiiice whereby the complete designation of the wanted line including theaoflice code and numericalport-ions thereof is, transferred from V the registers of the sender shown in Fig. 6 to the tandem sender 320,

When switch 200 operated a circuit was completed from battery throughvthe right contacts of relay 303-, thence over the tip side of trunk 4264 througlrcontacts of switch 200, contacts of switch 250, front contacts of relay 7 01, returning thijrough contacts of switch 250, over the tip conductor of trunk 161., 0011- tacts of switches and 15.0,, left inner con t acts of relay 401, right back contacts of re- 419, winding of relay 409,1left contacts of relay 419, left-outer contacts of relay 401, returning over'the ring side of trunks 161,

contacts or switch 250, conductor 7 53, outer back contacts of relay 7 02, inner front contacts of relay 703, winding of relay 706, conductor 756, contacts of switch 25,0, ringconductor of trunk 264 to ground at the left contactswof relay Relay 7 06- operate because of the polarity of the current in this circuit.- lVlien relay (420 has completely retracted its arinatures, the circuit hereinhefore'traced :is completed for operating relay 418, and when-the sender at the tandem office has beena-ytached to trunk 264, relay is energized thus causing the release of relay 409 at the originating ofli'ce. The releasecofvrelay 409 causes relay 419 :to operatein series with relay 418. l Vithrelay 419 operated acircuit is completed from battery through the right winding of relay 423, right contacts of relay 425', left inner eontaf-ts of 626, left front contacts of relay 614, front contacts of relay 4.18 to through the hack contacts of relay 420. Relay 423 completes an operating circuit for relay 403 which'in turn causes relay404 to.operate and lock, in turn closing a locking circuit for relay-423.-' Withv relay 404 opground ion does not resistance 671.

erated, a circuit is closed from battery through the winding of. relay 628, right outer baclrcontacts of relay 632, conductor 481, left outer front contacts of relay 429, right front contacts of relay 410, right outer front contacts of relay 625, right front contacts of relays 627 and 429, contacts of relay 426 to ground at the armature of relay 404. Relay 628 locks in series'with the winding of relay 426, the latter relay remaining normal. As hereinbefore described, relays 412 and 413 undergo their cycles of operationand release and impulses corresponding to the first digit of the office code are transmitted to the receiving relays ofth e tandem sender 320. Since register relay 631 is normal no numerical impulse is transmitted during the first impulse period. At the end of the first period, relay 406'operates and reverses the connection of the tip and ring conductors. During thesecond period, relay 632 being normal, no numerical impulse is sent. However, a circuit is completed from battery through the highresistance 671, left outer front contacts of relay 406, thence by means of. a circuit hereinbefore described in detail over the ring side of trunk 161 and 261, through contacts of switch 250, conductor 753, right outer contacts of relay 702, inner front contacts of relay 703, winding of relay 706, conductor 756, returning by means of switches 250 and 200 to the-ring conductor of trunk 264, left front contacts of relay 303, contacts of sender selector switch 310, through impulse receiving relays in sender 320 (these relays being similar to relays 705, 708 and 709) returning through switch 310, right front. contacts of relay 303, tip side of trunk 264, contacts of switches 200 and 250, conductor 757, front contacts of relay 701, conductor 759, contacts of switch 250, tip conductor of trunk 161, to ground at relay 419 as already traced. Relay 7 06 being of the comparatively low resistance type is enabled to operate in series with the high The operationof relay 706 to the winding of relays 707 extends ground 710 alone operating. As

and 710, relay noted hereinbefore, this light negative im-' the end of the second and fourth pulsing periods. When relay 710 is thus operated, a circuit is completed from battery through the winding of relay 721, back contacts of relay 722, left front contacts of relay 713 and 714, left front contact of relay 710 to the grounded conductor 751. Relay 721 immediately locks in series with the winding of relay 722 to the grounded conductors 751 but relay 722 is meanwhile shunted and fails to operate. At the end of the second impulse period, relay 406 releases thus causing the release of relay 706 whereby the shunt is removed from relay 707 which now operates in series with relay 710. VVhenthe light pulse is sent at negative impulse is sent during the fourth period, relay 707 remains locked but relay 710 is. shunted and releases. At the completion of the fourth period when relays 406 and 706 release, the locking circuit of relay 7 07 is broken which thereupon releases, removing the shunt from around the winding of relay 722 which now operates in series with relay 721. It is to be noted that these light negative impulses are not of a numerical nature but are sent to transfer the control of the impulse receiving relays in sender 310, as well as relays 707 and 710, to the successive registers. it will be understood that other code impulses are sent during the various periods in accordance with the set 726, 719 and 720, etc., in conjunction with the pulse counting relay 706 serve to count off the transmission of impulses to the tandem sender. t will be observed that because the receiving relays 705, 708 and709 are ineffective during these latter operations. the transmission of impulses corresponding to the setting of the thousandths register 640, and the succeeding numerical registers 670. has no effect on registers 750, .740, 730, etc., the transmitted impulses causing the set ting of the corresponding registers of the tandem sender 320. "W hen the complete record has thus been transmitted tothe sender 320, relay 7 58 is operated closing an obvious circuit for relay 702. The operation of relay 7 02-serves to bring about the release of the sender shown in Fig. 7, the marker shown in the upper right hand corner of Fig. 5, sender connector 571, connectors 230 and 240, sender selector switch 250 and the vertical magnets 216 and 217. Connection through switch 200 is maintained by the continued energization of the horizontal magnet 218 which is locked to the grounded sleeve conductor of trunk 264. When the complete record of the called line is registered in the sender 320, the sender connector 330 is operated and associates an idle marker 340 with the said sender. The record of the ofll-Ce code in sender 320 is thereupon transferred to corresponding registers in the marker 340 and is therein translated whereby a particular group of trunks inclu ding trunk 364 leading to the called ofiice is marked for selection. At this time also, frame connector 860 and trunk connector 370 are actuated, and marker 340 

